A. Technical Field
The present invention relates to a reaction method by using a heterogeneous catalyst such as an ion-exchange resin particle as a catalyst, and a reaction apparatus used in this reaction method. More particularly, the present invention aims, for example, reactions for producing (meth)acrylate by use of (meth)acrylic acid.
B. Background Art
Reaction methods which involves carrying out a reaction in liquid phase by using an ion-exchange resin as a catalyst, are known as a method (fixed bed reaction method) which involves using a reactor fix-packed with an ion-exchange resin or a method (fluidized bed reaction method) which involves canning out a reaction in a state that the ion-exchange resin is suspended and dispersed in a reaction liquid, and separating the reaction liquid and the ion-exchange resin after the reaction.
It is believed that the fluidized bed reaction method is preferable because its reaction efficiency can be improved.
JP-A-54326/1974 proposes a method which involves introducing a gas from the bottom of a reactor so that an ion-exchange resin can be suspended and dispersed in a reaction liquid, and separating the reaction liquid and the ion-exchange resin by use of a catalyst-separating apparatus comprising a filter. In addition, JP-A-17844/1988 proposes a method which involves suspending and dispersing an ion-exchange resin in a reaction liquid by use of stirrer, and separating the reaction liquid and the ion-exchange resin by use of a wire mesh of 80 mesh placed at the bottom of a vessel.
In the fluidized bed reaction method among the above conventional methods, when carrying out the separation of the ion-change resin and the reaction liquid by use of the filter or the wire mesh, the filter or the wire mesh is clogged with such a cracked ion-exchange resin during the reaction or a side-produced polymer in the reaction. Therefore, it becomes difficult to operate for a long time and the cracked ion-exchange resin becomes easily leaked.
For example, in case of the reaction to produce (meth)acrylate by allowing (meth)acrylic acid to react with alcohols, there was a problem that the hydrolysis was further caused by the ion-exchange resin as leaked. In addition, when the above reaction was continuously carried out, there was a problem that the effective resin amount was deceased with the passage of time and the reaction rate was lowered because of ununiform flow caused by such clogs. A sedimentation method is considered as effective means of separating the ion-exchange resin from the reaction mixture. However, the apparatus becomes larger according to this method. In addition, there is a defect that it takes much time to separate them.
In addition, in the conventional means of separating the ion-exchange resin and the reaction liquid in the above way, the piling portion of the ion-exchange resin and the reaction liquid is caused when carrying out the separation. Therefore, the reaction further proceeds while piling. However, in this case, the reaction becomes heterogeneous because the liquid and the resin do not flow, and impurities increase because the side reaction goes ahead.
Particularly, in case of exothermic reactions such as a reaction to produce hydroxyalkyl (meth)acrylate by allowing alkylene oxide to react with (meth)acrylic acid, it is difficult to remove heat at the piling portion. Therefore, the extraordinary rise of temperature is caused. At the portion of high temperature, the polymerization of such as (meth)acrylic acid as a raw material or hydroxyalkyl (meth)acrylate as a product is easily caused, and furthermore the problem of the above clogs is caused.
In addition, in the fixed bed reaction method, the wire mesh is easily clogged with the resin having a small diameter or a side-produced polymer. At the clogged portion, it is difficult for the liquid to flow, and the reaction liquid is piled up. The, the effective portion to carry out the reaction becomes less. Because of causing the piling portion in the reactor, not only the reactivity lowers and the side reaction increases but also the polymerization of the raw material and the product is accelerated and the operation becomes difficult.
In reactions other than the reaction by using the ion-exchange resin, the same problem is also caused in the reaction method which involves carrying out a reaction in liquid phase by using various heterogeneous catalysts.
An object of the present invention is that: when carrying out a separation of a heterogeneous catalyst and a reaction liquid, the separation of the heterogeneous catalyst and the reaction liquid can be carried out certainly and effectively by using a compact apparatus with inhibiting the side reaction or the polymerization and avoiding unstable operation due to clogs of the heterogeneous catalyst.
A reaction method by using a heterogeneous catalyst, according to the present invention, is a method which involves carrying out a reaction in liquid phase by using a heterogeneous catalyst particle in a reactor, and comprises the steps of: (a) allowing a reaction liquid supplied into the reactor to react in the presence of the heterogeneous catalyst particle, and (b) passing the resultant reaction liquid containing the heterogeneous catalyst particle through a line screen having an opening width where the heterogeneous catalyst particle is not allowed to pass substantially, and then extracting the reaction liquid separated from the heterogeneous catalyst particle from the reactor.
The present invention aims liquid-phase reactions, and does not aim gas-phase reactions.
The term xe2x80x9ca line screen having an opening width where the heterogeneous catalyst particle is not allowed to pass substantiallyxe2x80x9d means that the heterogeneous catalyst particle which passes through the line screen may exist in an amount which does not affect attaining functions and effects of the present invention because the heterogeneous catalyst particle as industry used has particle distribution without fail.
The opening width of the line screen is determined so that the ratio of particles which pass through the line screen can be ordinary not more than 5 volume %, preferably not more than 2 volume %, more preferably not more than 0.3 volume %.
In addition, the 15% particle diameter is defined as the diameter when the particle distribution in terms of volume becomes 15% at the small particle side, and it is effective that the opening width of the line screen is determined narrower than the above 15% particle diameter. The lower limit of the opening width of the line screen can be determined in the larger size of {fraction (1/25)} of the 15% particle diameter or 0.05 mm. In case where the opening width is narrower than the above size, there are disadvantages in long-time operation because the screen is easily clogged with even a small amount of such as small fragment of the catalyst particle, and the screen filled with the small fragment in the above way is with difficulty washed.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.